A neutral to ground short would not cause the breaker to trip; indeed, bonding neutral to ground is shorting them together, by definition. They're expected to be at the same potential (if bonded). The short would cause an upstream GFCI to trip.
If your ground to neutral bond is broken or lacking, your generator output is floating and most any arbitrary voltage between hot or neutral and ground is not unexpected. The voltage between hot and neutral is what matters for appliances. In that case it makes little sense to reference your measurements to ground since the voltage being generated is not referenced to ground (or anything else). Similarly, a broken or bad ground connection between the generator and the RV would cause the output to float...but that in itself wouldn't cause the air conditioner and microwave to have trouble.
